1. Field of the Invention
The present invention relates generally to reflectors and, more particularly, to reflectors for coupling light from a light source into one or more light guides.
2. Description of Related Art
Large diameter fiber optics, often referred to as "flexible light guides", are well known in the art, and typically comprise a single, solid core light guide which is surrounded by a cladding layer and a sheath or shielding layer. The core is the portion of a light guide which transmits light, and typically has a diameter of about 2 to 12 mm. It is formed of a very soft, semi-liquid plastic material, such as OPTIFLEX.RTM., which is manufactured by Rohm & Haas Corporation, of Philadelphia, Pa. The cladding layer typically comprises polytetrafluoroethylene (PTFE or TEFLON.RTM.), or the like, while the outer sheath is fabricated of a material such as polyvinylchloride (PVC). Unlike small diameter light guides, which are typically used to transmit information in relatively complex control systems, these large diameter "light guides" are typically employed in a variety of illumination systems where direct lighting is difficult to maintain, dangerous, or subject to vandalism. Examples include architectural lighting, display cases, pools and spas (to eliminate electrical connections near water), hazardous material zones (to eliminate the need for sealed lighting), and jail cells. Large diameter light guides are particularly advantageous in that only a single centralized illumination system must be maintained, rather than a plurality of individual lights.
There are problems, however, in implementing state of the art light guide illumination systems because of the difficulty of illuminating a plurality of light guides from a single illumination source, as is discussed in related application Ser. No. 08/374,163. According to one prior art configuration, the light guides are bundled as closely as possible, to ensure the maximum ratio of core area (the part of each light guide which actually transmits light) to total area. However, bundling the large diameter light guides together in order to illuminate them from the single illumination source is difficult to do efficiently. The individual light guides are round and thus have a great deal of space between them due to the cladding and shielding layers. To obtain maximum efficiency, it is desirable to illuminate only the core of each of the bundled light guides, but this is impossible using state of the art bundling techniques. Necessarily, if the light from the source of illumination is spread across the array of light guides, it will illuminate not only the cores of the light guides, but also the cladding layers and shielding layers. Furthermore, the voids between the light guides, which are inevitable because of the light guides' round dimensions, also are impacted by the light from the illumination source. All of the light falling upon any element other than the cores is wasted, and becomes an efficiency loss, since it will not be transmitted by the light guides. Additionally, packing the light guides closely together creates problems such as mechanical difficulties in configuring and accommodating the illumination system and difficulties encountered in attempting to replace one of the individual bundled light guides. This design also typically results in color variation between light guides unless techniques are specifically employed to prevent this problem.
One prior art solution to this problem has been to eliminate the sheathing and cladding layers about each light guide, in order to reduce the area across the bundled array of light guides which does not transmit light. However, there is still a packing factor problem because the light guides are round, and there are other physical disadvantages in eliminating those layers. Thus, this solution is unsatisfactory for most applications.
A number of prior art approaches use reflectors for focussing light from a source of illumination into one or more light guides. U.S. Pat. No. 5,222,793 and U.S. Pat. No. 5,259,056, both to Davenport et al., disclose lighting systems which use a single reflector assembly for illuminating light transmissive elements. U.S. Pat. No. 5,396,571 to Saadatmanesh et al. discloses a multi-segmented lens which divides light from a light beam into four separate beams, each of which is focussed onto a separate optical fiber. U.S. Pat. No. 4,912,605 to Whitehead discloses an electric light source mounted between two reflectors, each of which directs light into a corresponding light guide. U.S. Pat. No. 5,469,337 to Cassarly et al. discloses a light source and a plurality of curved reflectors for focussing light into lenses and then into a plurality of light guides. The use of reflectors and multi-segmented lenses by the prior art for coupling light into light guides has represented some advancement over the prior art bundled light guides, but the need for a proper and efficient coupling of a light source to a plurality of light guides still remains.
In many cases the proper and efficient coupling of a light source to a plurality of light guides changes according to the particular light source being used. Modern electrodeless lamps, for example, which burn very brightly, can be too powerful for coupling to only one or two light guides. If an inefficient coupling is used the effective luminosity may be reduced for a better match with the light guides, but the cost of running the system will then be unreasonably high as a result of the wasted energy. Efficiency is still desired so that the energy associated with generating the high luminosity of such a bright illumination source can be fully utilized.
Another problem associated with prior art designs is the large number of optical components associated with these designs. Reducing the number of parts of any optical design would appear to be advantageous to any system.